Intravenous (IV) cannulation is a routine procedure for most hospital patients for drug or fluid administration. Successful delivery of drugs and fluids depends on the cannula remaining in the vein at all times. Extravasation refers to the accidental leakage of IV drugs from the vein to the surrounding tissues. This can occur for a variety of reasons such as (1) incorrect placement of the cannula, (2) fragile veins (especially in infants and the elderly), (3) excessive movement from the patient resulting in the cannula being pulled out and (4) excessive pressure from the infusion pump used to infuse fluids, damaging the vein or dislodging the cannula. Extravasation begins with the drug accumulating in the subcutaneous tissue distal to the cannula, creating a bulky area. Complications related to extravasations may be quite severe and may include irritation, congestion, blistering and even necrosis of the tissue. Severe cases may result in prolonged hospital stays, cosmetic defects, functional impairment and require reconstructive surgery to repair.
Extravasation is frequently detected late when a large subcutaneous “bump” is noticed at the IV cannulation site, indicating that a large amount of infused fluid has infiltrated the surrounding tissues. This is a particular problem in the operating room with anaesthetized children, as it is often impossible to visualize the cannula site when patients are under surgical drapes. The severity of extravasation injury depends on the volume/type of drug extravasated and the time lapse before the extravasation is detected. It is important to detect extravasation early for two main reasons. Firstly, early detection will limit any potential damage to the surrounding tissues. This is of crucial importance during infusion of vesicant drugs which cause tissue destruction or irritant drugs which in turn cause pain or inflammation in the tissues. Secondly, early detection of extravasation will ensure that the drugs/fluids administered will reach the patient's intravascular space as intended, failure of which can jeopardize medical management and compromise patient care.
Currently available devices to detect extravasation are expensive, bulky, cumbersome and not for routine use. The occlusion alarms provided by conventional infusion pumps are neither sensitive nor specific enough to detect extravasation. Occlusion pressure limit cannot reliably detect extravasation especially at sites with high compliance, low flow rates, even when pump is set to low occlusion limits.
One available extravasation detector utilizes radio frequency wave (RF Wave) technology to prevent moderate to severe extravasation. It is incorporated into an injection system and stops injection when pooling of fluid is detected under the patient's skin. However, this system is expensive, cumbersome and impractical for detecting early extravasation.
An extravasation detector based on microwave radiometry has also been presented. It relies on temperature differentials in the region of accumulated fluids and is able to detect very small volumes of fluid extravasation. However, the sensor may be too sensitive, leading to frequent false alarms.
Ultrasound Doppler sensor has also been used to measure blood flow velocity in the vein for extravasation detection. If the cannula is properly sited and the contrast medium flows as desired along the vein, this will lead to an increased flow velocity in the vein.
Another available extravasation detection system, as part of a contrast injection system, comprises an electrode patch with an embedded sensor. It pauses injections if a clinically significant variation is detected and is useful only at high flow rates. It detects large volumes of extravasation and is not sensitive enough to detect early extravasation. The electrode patches need to contact with patient's skin to measure the tissue impedance when extravasation occurs.
Another device is a transducer embedded in a fixture to detect extravasation. The transducer can sense the normal force caused by skin swelling. However, it is difficult to detect shear force caused by skin stretch during low infusion rate (<10 ml) cannulation.
There is therefore an urgent clinical need for a small, portable, practical and cost-effective device to detect early extravasation, and which may trigger a warning, may be independent of rate of infusion and which can be universally applied to all patients.